THE CHARGE TRANSPORT IN A SILICON RESISTOR AT LIQUID-HELIUM TEMPERATURES

A simple, one-dimensional model describing the steady-state charge transport in a silicon n+nn+ (p+pp+) resistor at liquid-helium temperatures is derived. This model includes both space-charge and (contact) barrier limitations to the current flow, typically occurring at these temperatures (T<30 K) in Si. Furthermore, account is made for the interactions between the injected free carriers and the shallow doping atoms, i.e., mainly trapping and shallow level impact ionization, yielding breakdown of the material at rather low electrical fields F. Good qualitative agreement with measured current-voltage characteristics is found. In addition, the model is able to describe the flow of avalanche-generated current through the substrate/well of a metal-oxide-semiconductor transistor, which is essential for developing a truly analytical description of the low-temperature drain current kink.